# Where Is Earth’s Largest Waterfall?

> The largest waterfall on Earth never breaks the ocean surface. It pours through the Denmark Strait between Greenland and Iceland, where a hidden wall of cold water descends along the seabed. The drop reaches roughly 11,500 feet, more than three times the...

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Published: 2026-09-01T14:23:51+00:00
Categories: Explainer, Oceans

![NOAA diagram showing the underwater waterfall beneath the Denmark Strait](https://www.argo.net/wp-content/uploads/2026/09/noaa_denmark_strait_underwater_waterfall.jpg)

The largest waterfall on Earth never breaks the ocean surface. It pours through the Denmark Strait between Greenland and Iceland, where a hidden wall of cold water descends along the seabed. The drop reaches roughly 11,500 feet, more than three times the height of Angel Falls and the flow carries far more water than any river waterfall.

[NOAA's description](https://oceanservice.noaa.gov/facts/largest-waterfall.html) places the cataract beneath a busy gateway between the Nordic seas and the North Atlantic. Ships can cross above it without seeing foam or spray. Oceanographers detect the descent through temperature, salinity, pressure and current measurements because the entire event takes place inside another body of water.

The feature also differs from an isolated geological oddity. Water reaching the ridge has already been cooled and transformed across the Nordic seas. After descending, it joins deep currents that continue far beyond the strait. The [UK Met Office](https://www.metoffice.gov.uk/research/climate/cryosphere-oceans/ocean-circulation) describes the ocean's overturning circulation as a connected movement influenced by density differences and winds. Denmark Strait supplies one concentrated passage within that larger network.

Numbers quoted for the cataract can vary among descriptions because scientists may define its upper and lower boundaries differently. NOAA's infographic gives a height near 11,500 feet, while its text describes a descent beginning around 2,000 feet below the surface and reaching toward 10,000 feet south of Greenland. Both convey the same physical scale: a submerged drop measured in miles, spread across a channel rather than concentrated at one cliff edge.

## How scientists define the waterfall record

The record depends on what scientists mean by a waterfall. On land, water crosses a lip and falls through air before reaching a lower river or pool. In the Denmark Strait, the moving fluid remains surrounded by seawater, yet the same basic forces are present. A denser layer approaches a ridge, crosses its crest and accelerates down a steep slope under gravity. Oceanographers often call such a feature a cataract or overflow. The terms describe a current with a large vertical descent rather than a scenic column of falling water.

Its scale is easier to grasp through measurements than photographs. The cataract extends across a broad section of the strait and its upper boundary can shift as the current pulses. The fastest water hugs the bottom while mixing creates a more gradual boundary above it. No single point contains the whole waterfall in the way that one cliff contains a land cascade. The record refers to the combined submarine system, including its enormous drop and sustained transport of dense water.

## The Denmark Strait cataract holds the record

The **Denmark Strait cataract** begins where relatively cold water flowing south meets warmer Atlantic water. Its immense vertical reach comes from the undersea terrain. A ridge across the strait holds back dense Nordic water until it spills over the ridge and follows the continental slope toward deeper parts of the Atlantic.

NOAA estimates the descending current at more than 123 million cubic feet per second. The figure describes a broad, persistent flow rather than a narrow ribbon like Niagara Falls. The cataract is about 2,000 feet below the surface at its upper edge, then continues toward depths near 10,000 feet south of Greenland.

Angel Falls in Venezuela drops 3,212 feet and remains the tallest uninterrupted waterfall on land. Comparing the two requires some care because an ocean cataract has no free-falling sheet exposed to air. Scientists use the familiar word waterfall because dense water crosses a major topographic step and accelerates downward under gravity.

## Density makes an underwater waterfall possible

Seawater density changes with temperature and salinity. Colder water usually packs more mass into the same volume, while added salt also raises density. The Nordic seas lose heat to the atmosphere during winter, producing water dense enough to sink and spread through deep channels. The [Woods Hole Oceanographic Institution](https://www.whoi.edu/know-your-ocean/ocean-topics/how-the-ocean-works/ocean-circulation/) explains how such density differences help drive deep circulation.

In the strait, the **heavy southbound layer** approaches the ridge below a lighter northbound current. Gravity pulls the lower layer across the sill. Once over the crest, the water plunges down the slope, speeds up and mixes around its edges. The boundary between the layers can resemble a moving front even though both sides are seawater.

The descent belongs to a family of flows called **overflow currents**. Similar overflows occur through the Faroe Bank Channel and other passages linking the Nordic seas with the Atlantic. Their depths, rates and routes depend on the shape of the seafloor, which channels dense water much as a valley guides a river.

Turbulence strips small parcels from the overflow and blends them with surrounding Atlantic water. Mixing makes the current warmer and less salty as it travels. Researchers therefore follow changes in temperature and salinity to distinguish its core from water picked up along the route.

## Scientists measure a waterfall they cannot see

Oceanographers lower instruments known as **CTD packages** to measure conductivity, temperature and depth. Conductivity provides information about salinity, while pressure reveals depth. A line of CTD profiles across the strait produces a vertical picture of the water masses, including the cold dense layer pressed against the bottom.

Anchored moorings add the time dimension. Current meters positioned at several depths record speed and direction through seasons and storms. The [Global Ocean Observing System](https://www.ocean-ops.org/board?t=goos) coordinates many observing networks that track the physical state of the sea, although conditions in narrow, deep passages still require dedicated regional instruments.

Research vessels also use **acoustic Doppler current profilers**. These devices send sound pulses into the water and infer motion from echoes returned by drifting particles. Repeated ship sections show how the overflow changes across the channel. Autonomous floats can follow water downstream, but steep terrain and powerful currents make the core difficult to sample continuously.

Satellites cannot look directly through thousands of feet of seawater. They can measure sea-surface height, temperature, ice cover and winds that influence the system. Underwater observations remain essential because the key boundary lies close to the seabed.

Measurements carry uncertainty because the current pulses and shifts. A single crossing captures one moment. Long records are needed to separate weather-driven fluctuations from lasting changes in the volume of dense water passing through the strait.

## The cataract feeds the Atlantic's deep circulation

Water crossing the Denmark Strait becomes part of **North Atlantic Deep Water** after it mixes with neighboring water masses. It then spreads through the deep Atlantic. The larger circulation transports heat between regions and moves dissolved carbon, oxygen and nutrients through the ocean interior.

The [NASA overview of ocean circulation](https://www.nasa.gov/earth/oceans/ocean-circulation/) describes how wind-driven surface currents connect with density-driven movement at depth. Denmark Strait overflow supplies one important branch of that global system. Calling it the largest waterfall emphasizes its scale, while its broader scientific value comes from the water it transfers between ocean basins.

Climate can influence the source water through air temperature, sea ice, precipitation and freshwater entering the Nordic seas. Scientists monitor the overflow to learn whether its properties or volume are changing. A shift would not translate directly into an immediate climate outcome, since the Atlantic circulation includes many pathways and feedbacks.

The hidden cataract reveals how strongly **seafloor geography** governs the ocean. A ridge that no observer can see from a ship forces a vast current downward, stirs layers together and helps set the properties of deep Atlantic water. Earth's waterfall record therefore belongs to an ocean process measured by instruments rather than a landmark visible from shore.

**Related reading:** [surface and deep-ocean currents](https://www.argo.net/surface-currents-vs-deep-ocean-currents/) and [how scientists measure ocean currents](https://www.argo.net/how-do-scientists-measure-ocean-currents/).

 **Explore this topic:** [What Are the Seven Seas?](https://www.argo.net/what-are-the-seven-seas/) and [Is There Gold in the Ocean?](https://www.argo.net/is-there-gold-in-the-ocean/).